Electronic music systems employing a computer which receives and processes musical information are known. However, known systems suffer from a number of drawbacks which render them unsuitable for general use in certain interactive applications such as learning applications.
For example, certain systems such as keyboard systems may use key actuated switch closures to generate signals representing musical information. In such systems, the input device is not in fact a traditional musical instrument but is a keyboard which directly provides computer-usable data outputs and simulates a keyboard instrument.
Various approaches have been used to create electronic music systems in which the input device is not a traditional keyboard, but is a device simulating a musical instrument. For instance, various guitar-like devices have been made which utilize contacts actuated by playing the instrument in order to generate signals representing such playing. Such devices are not truly musical instruments, but merely are dedicated computer input devices which function similar to but are shaped differently than an ordinary keyboard.
Various other attempts have been made to mate a guitar-like musical input device with a computer system. For instance, special-purpose guitars have been constructed in order to provide a computer input more nearly corresponding to the output of a guitar. For example, guitars have been constructed using strings all of the same gauge which are tuned to high frequencies; this provides ease of detection of string and fret data, but precludes playing without the computer. Such guitars have been typically designed to communicate with a computer via a MIDI interface (Musical Instrument Digital Interface). Such special purpose guitars have not been well received, in part because construction features necessary for prior art methods of signal acquisition render these guitars substantially different from ordinary guitars, and guitarists may be unwilling to purchase an additional guitar solely for the purpose of providing an input to a computer system. Moreover, the MIDI interface is not well suited to use with real guitars, because it is based on real time signal processing, and real time conversion of guitar notes to MIDI data is difficult and expensive.
The MIDI interface is designed to enable the coupling and coordination of a large number of instruments and computers. The MIDI protocol is an effort to provide a standard interface between instruments and computers, so that any MIDI instrument can be coupled to any MIDI computer. However, the MIDI protocol includes certain features which render it extremely difficult to make a converter which provides a MIDI output from a real guitar, and any modification of the protocol to facilitate the interchange of data between a guitar and a computer would remove the protocol from standard MIDI.
In particular, MIDI devices are synchronized by a common system timing clock, such as a sequencer or a drum machine. MIDI messages include "Note On", which when transmitted includes the key number or other frequency information for the note being played. Thus, frequency information must be available when a MIDI "Note On" message is to be transmitted, which may be an extremely short time after the note is played. This poses no problem for typical MIDI instruments such as keyboards, in which frequency information is inherent in the key which is struck. However, for real instruments such as guitars the only way to quickly provide frequency information is with high speed converters, which are complex and expensive. Simpler, low cost techniques such as timing the period of the note played take too long to provide MIDI data when a note, particularly a low note, is struck.
Moreover, MIDI systems are typically essentially synthesizers where the instrument being played is merely a controller and the sound which is created is synthesized by a computer.